Document Security Utilizing Color Gradients

ABSTRACT

The present invention includes apparatus and methods for printing and verifying postage stamps on demand via a personal postage stamp printer. The indicium by which the stamp is printed includes a color stripe and a data field including authentication data that corresponds to the color stripe. To authenticate the stamp, the authentication data in the data field is read and compared with authentication data extracted from the color stripe.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional Application of co-pending applicationSer. No. 10/990,719 entitled “Document Security Utilizing ColorGradients” which is a continuation-in-part of prior co-pendingapplication Ser. No. 10/819,700 entitled “Postage Indicia IncludingColor Bar Sequence to Aid In Authentication” filed on Apr. 7, 2004,which is a continuation-in-part of prior co-pending application Ser. No.10/645,376 entitled “Postage Indicia Including Encoded InkCharacteristic Data”, filed Aug. 21, 2004. All of the prior applicationsare incorporated herein by reference in their entirety.

BACKGROUND

This invention relates generally to the field of document security, andmore particularly to printing and reading of document components tosafeguard and verify the authenticity of a document.

It has been proposed to provide postage stamp printing devices that maybe used by postal patrons to print their own postage stamps. However, itis an important consideration that counterfeiting of such postage stampsbe deterred. More generally, it is desirable to provide printed securityelements that are suitable for deterring counterfeiting of a widevariety of documents.

SUMMARY

Accordingly, apparatus and methods for printing and inspectingmachine-verifiable documents such as postage stamps are provided.

In one aspect, a method includes providing authentication data. Themethod further includes printing on a substrate a first representationof the authentication data, and printing on the substrate a secondrepresentation of the authentication data. The first representationincludes a color region that represents the authentication data by avariation of at least one color component of the color region.

The variation may be substantially continuous, and may be periodic, suchas sinusoidal. Both the first and second representations may be part ofa postage meter indicium. As used herein, the term “postage meterindicium” should be understood to include, but not be limited to, apostage stamp printed by a personal postage stamp printer.

The substrate may be an envelope or a medium used for printing ofpostage stamps by a personal postage meter.

The first representation of the authentication data may be in the formof a color stripe. The second representation of the authentication datamay be in the form of a barcode such as a two-dimensional barcode. Thefirst and second representations may be printed on the substratesubstantially simultaneously. More generally, the second representationof the authentication data may be in the form of any machine-readablesymbology including a two-dimensional barcode, a one-dimensionalbarcode, or an OCR (optical character recognition) font.

In another aspect, a method of authenticating a document includesscanning at least a portion of the document. The method further includesanalyzing a color region of the scanned portion of the document todetect first authentication data represented by a variation of at leastone color component of the color region. The method also includesreading a second region of the scanned portion of the document to detectsecond authentication data. In addition, the method includes comparingthe first and second authentication data.

The variation of the at least one color component may be substantiallycontinuous, and may be periodic, such as sinusoidal. The document may bea postage meter indicium. The second region may include a barcode suchas a two-dimensional barcode.

In still another aspect, a method includes scanning a color stripe andgenerating color gradient data indicative of at least one characteristicof a variation in intensity of at least one color component along thelength of the color stripe.

The method may further include reading a barcode adjacent to the colorstripe to generate barcode data, and comparing the barcode data with thecolor gradient data. The color stripe and the barcode may both be partof a postage meter indicium, and the comparing step may be for thepurpose of authenticating the postage meter indicium. The barcode may bea two-dimensional barcode. The variation in intensity of the at leastone color component may be a sinusoidal variation, and the at least onecharacteristic indicated by the color gradient data may be at least oneof wavelength, amplitude and phase of the sinusoidal variation.

In another aspect, an apparatus includes a data mechanism for providingauthentication data, and a printing mechanism for printing on asubstrate a first representation of the authentication data and a secondrepresentation of the authentication data. The second representationincludes a color region that represents the authentication data by avariation of at least one color component of the color region.

In still another aspect, an apparatus for authenticating a documentincludes a mechanism for scanning at least a portion of the document, amechanism for analyzing a color region of the scanned portion of thedocument to detect first authentication data represented by a variationof at least one color component of the color region, a mechanism forreading a second region of the scanned portion of the document to detectsecond authentication data, and a mechanism for comparing the first andsecond authentication data.

In yet another aspect, a substrate (e.g., an envelope or an item ofadhesive label stock) has printed thereon a first representation ofauthentication data and a second representation of authentication data.The second representation of the authentication data includes a colorregion that represents the authentication data by a variation of atleast one color component of the color region.

In accordance with some aspects of the invention, postage indicia may beprinted on adhesive label stock to form postage stamps. Each indiciummay include a color stripe, which may vary from indicium to indicium.Variations such as gradients in one or more color components in thecolor stripe may be used to represent authentication data. Each indiciummay also include another representation (e.g., in a two-dimensionalbarcode) of the authentication data. The authenticity of the indiciummay be verified by scanning the indicium and then (e.g., automaticallyby machine) comparing the authentication data represented by the colorstripe and by the other representation. Thus the presence of theseelements in a postage indicium may help to deter counterfeiting. Thecolor stripe may include subtle gradients that are not readilydetectable or reproducible, to provide an additional layer of security.

Therefore, it should now be apparent that the invention substantiallyachieves all the above aspects and advantages. Additional aspects andadvantages of the invention will be set forth in the description thatfollows, and in part will be obvious from the description, or may belearned by practice of the invention. Various features and embodimentsare further described in the following figures, description and claims.

DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate presently preferred embodiments ofthe invention, and together with the general description given above andthe detailed description given below, serve to explain the principles ofthe invention. As shown throughout the drawings, like reference numeralsdesignate like or corresponding parts.

FIG. 1 is a block diagram that illustrates a consumer postage stampprinting apparatus arranged in accordance with principles of the presentinvention.

FIG. 2 is a block diagram that illustrates an administrative server thatis part of the apparatus of FIG. 1.

FIG. 3 is a block diagram that illustrates a postage stamp printer thatis part of the apparatus of FIG. 1.

FIG. 4 illustrates a postage stamp printed in accordance with principlesof the present invention, shown in juxtaposition with a print head forprinting the postage stamp.

FIG. 5 shows on a larger scale a color stripe that is part of thepostage stamp of FIG. 4.

FIG. 6 is a graph that illustrates variations in two color componentsalong the length of the color stripe of FIG. 5.

FIG. 7 is a flow chart that illustrates a process that may be performedby the apparatus of FIG. 1.

FIG. 8 is a block diagram of a device that may be provided in accordancewith principles of the present invention to verify the authenticity ofthe postage stamp of FIG. 4.

FIG. 9 is a flow chart that illustrates a process that may be performedby the verification device of FIG. 8.

DETAILED DESCRIPTION

The present invention includes apparatus and methods for allowing apostal customer to print his or her own postage stamps. The stamps areprinted using a personal postage stamp printer. The stamp printer printson adhesive label stock. The postage indicium printed to form the stampincludes a color stripe. Variations such as color gradients in the colorcomponents of the color stripe represent authentication data. Thepostage indicium also includes another representation of theauthentication data. This other representation of the authenticationdata may present the data in encoded (and possibly also encrypted) formin a two-dimensional barcode or in another form. The color stripe andthe 2D barcode vary from stamp to stamp. The 2D barcode is downloaded tothe postage stamp printer from an administrative server, which handlescharging of the postage to the customer's account.

To verify the stamp, the stamp is scanned and machine analysis isperformed to detect the color component variations along the colorstripe and to read the authentication data encoded in the 2D barcode. Ifthese two pieces of information match, the authenticity of the stamp maybe considered to be verified.

Referring now to the drawings, and particularly to FIG. 1, the referencenumeral 10 indicates generally a postage stamp printing apparatus inaccordance with principles of the present invention. The apparatus 10includes a personal postage stamp printer 12 (hereinafter, “printer 12”)shown in data communication with a postage funds administrative server14. While the description of the preferred embodiment shows a particulardivision of steps in the process of creating an indicium employing colorgradients, any other division of steps is within the scope of theinvention. In one embodiment, the printer 12 may be a postage meter thatcan perform all the functionality. In another embodiment, the printer 12could provide the ability to format the barcode and/or the color stripeand receive only the security data from the administrative server 14.

Both the printer 12 and the server 14 will be described in more detailbelow, but their functions will now be generally described. The printer12 prints postage stamps on demand by the postal customer that haspossession of the printer. The printer may operate independently of theserver to print a stamp while not connected to the server. The server 14handles charging the customer's account for postage corresponding tostamps authorized to be printed by the printer 12. The server 14 alsogenerates and downloads to the printer 12 security-related informationto be included in the images printed to form the postage stamps.

The printer 12 may be in occasional data communication with the server14 via, for example, a dial-up connection and/or the Internet.

FIG. 2 is a block diagram that illustrates an embodiment of the server14 shown in FIG. 1. Generally, in some embodiments, the server 14, inits hardware aspects, may be constituted by conventional computerhardware. As seen from FIG. 2, the server 14 may include a processingunit 20. The processing unit 20 may be constituted by one or moreprocessors of the type used in server computers, mainframe computers,minicomputers and/or desktop computers. The server 14 may also include acommunication device 22 in communication with the processing unit 20.The communication device 22 may, for example, comprise one or more datacommunication ports by which the processing unit 20 may exchange datawith the printer 12 (FIG. 1) and/or with other personal postage stampprinters. (Although only one printer is shown in FIG. 1, it should beunderstood that the server 14 may, at any one time or at various times,be in communication with a number, and potentially a large number, ofdifferent personal postage stamp printers.)

The server 14 may further include an output device 24 in communicationwith the processing unit 20 and an input device 26 in communication withthe processing unit 20. The output device 24 may, for example, compriseone or more printers and/or one or more display monitors. The inputdevice 26 may include conventional devices such as a keyboard and/ormouse or other pointing device. The input device 26 may be used by ahuman operator to control, administer, maintain or provide input to theserver 14.

There may also be included in the server 14 a storage device 28 that isin communication with the processing unit 20. The storage device 28 maycomprise, for example, a combination of magnetic, optical and/orsemiconductor memory devices. In some embodiments, the storage device 28may include one or more hard disk drives, RAM (random access memory),ROM and one or more drives for removable data storage media.

The storage device 28 may store a number of programs for controlling theprocessing unit 20. For example, the storage device 28 may store serverfunctions software 30 that enables the server 14 to function as a hostto client devices such as the above-mentioned personal postage stampprinters that may be in communication with the server 14 from time totime. (In an alternative embodiment, a personal computer may beconnected to a personal stamp printer.)

The storage device 28 may also store postage funds handling software 32that enables the server 14 to handle charges to customer accounts inrespect of postage funds disbursed by printing of postage stampsauthorized by the server 14.

The storage device 28 may further store software 34 that enables theserver 14 to generate image data that corresponds to 2D barcodes to beprinted by the personal postage stamp printers as part of the postageindicia that form the stamps.

FIG. 3 is a block diagram that illustrates an embodiment of the printer12. The printer 12 includes a print head 50. The print head 50 may, forexample, be a color inkjet print head, or a thermal print head of a typesuitable for color direct thermal printing. The print head 50 mayinclude a first set 52 of print elements and a second set 54 of printelements. The first set 52 of print elements may be dedicated toprinting the color stripe portion of the postage indicia printed by theprinter 12. The second set 54 of print elements may operate to printother portions of the postage indicia. In some embodiments, the firstset 52 of print elements may consist of 16 adjoining print elements at alower end 56 of the print head 50, and the second set 54 of printelements may consist of approximately 280 print elements, being all ofthe other print elements of the print head 50. In some embodiments, theprint head may print at a density of about 300 dpi (dots per inch) toproduce indicia having a height of about one inch.

The printer 12 also includes a printer controller 58 that is operativelycoupled to the print head 50 to control the print head 50. The printercontroller 58 includes a print head controller 60 which is coupled tothe print head 50 and which provides the direct control of the printhead 50. The print head controller 60 may be constituted by suitableprocessing or control circuitry and may provide general controlfunctions for the printer 12.

The printer controller 58 may also include a ROM 62 which may store asequence of units of authentication data. Each unit of authenticationdata may be used to generate a respective color stripe as part of arespective postage stamp to be printed by the printer 12. Each unit ofauthentication data may, for example, be a string of data bits, and mayconsist of as little as a few data bits. In one embodiment, each unit ofauthentication data may consist of around two bytes to 18 bits of data,and may be represented in the corresponding color stripe by variationsalong the length of the color stripe in a single color component. Forexample, the color stripe may include superimposed sinusoidal variationsin the color component corresponding to, say, six wavelengths, withthree bits encoded in each wavelength as variations in phase and/oramplitude associated with each wavelength.

A portion (indicated at 64) of the print head controller 60 may bededicated (e.g., hard-wired) to control only the first set 52 of printelements, and to cause the print elements 52 to print only color stripesas defined by the units of authentication data stored in the ROM 62. TheROM 62 may be coupled to the dedicated portion 64 of the print headcontroller 60. A security perimeter 66 may be provided to prevent and/ordeter (and/or to provide evidence of) tampering with the ROM 62, thededicated portion 64 of the print head controller 60 and the printelements 52 to assure that the print elements 52 print only colorstripes defined by the data in the ROM 62. Alternatively the printercontroller may be capable of calculating a unit of authentication datafor each postage stamp according to an algorithm from a seed valuestored in ROM.

The printer controller 58 may further include a non-volatile RAM 68,which may be in communication with the print head controller 60. The RAM68 may operate as working memory and may also store image data, to bediscussed below, which is downloaded to the printer 12 from the server14 (FIG. 1) and which may be used to control the print head 50 to printone or more postage indicium elements prescribed by the server 14. Insome embodiments, RAM 68 may also function as program storage for aprogram to control the print head controller 60.

In addition, the printer controller 58 may include a modem 70 throughwhich the printer 12 may engage in data communication with the server14, a media motion control circuit 72 that controls feeding of asubstrate (e.g., an item of adhesive label stock, which is not shown inFIG. 3) past the print head 50, and a power supply 74 that providespower for at least part of the printer 12. The printer controller mayalso have a communication port (USB, serial, parallel, etc.) forcommunicating with a PC.

The printer 12 may also include other components which are not indicatedin FIG. 3. Such other components may include, for example, a housing, auser interface (e.g., one or more switches or buttons, a display, atouch screen, etc.), and mechanical components for transporting thestamp stock past the print head 50.

FIG. 4 illustrates a postage stamp 80 printed by the printer 12 inaccordance with principles of the present invention, and shown injuxtaposition with the print head 50 of the printer 12 (the balance ofprinter 12 is not shown in FIG. 4). The postage stamp 80 includes apostage indicium 82 formed on a substrate 84 (e.g., adhesive labelstock). In some embodiments, the substrate may be a type of stocksuitable for thermal color printing.

The postage indicia 82 may include a logo 86 and a data field 88 inwhich machine-readable data is printed. The data field 88 may, forexample, take the form of a two-dimensional barcode. Some or all of thedata field 88 may be printed in accordance with the “Information-BasedIndicia Program” (IBIP) promulgated by the U.S. Postal Service. The IBIPinformation may contain high-density variable cryptographicallyprotected information in a two-dimensional barcode. The IBIP informationmay be used for security and marketing purposes. As will be seen, thedata field 88 may also include data provided for security purposes(stamp authenticity verification purposes) in accordance with theprinciples of the present invention.

The postage indicium 82 also includes a color stripe 90, printed inaccordance with principles of the present invention. The color stripe 90may be printed by the print elements 52 of the print head 50, so thatthe color stripe 90 extends along the bottom of the postage indicium 82,adjacent to the logo 86 and the data field 88. The logo 86 and the datafield 88 are printed by the print elements 54 of the print head 50.

The postage indicium 82 also includes an alphanumeric data field 91 thatmay include alphanumeric information such as amount of postage, date ofprinting/mailing and location/zip code of mailing.

The postage indicium 82 is shown in FIG. 4 in juxtaposition with theprint head 50. The arrow mark 92 is indicative of the direction in whichthe substrate 84 is moved past the print head 50 to allow the first set52 of print elements to print the color stripe 90 while the second setof print elements 54 print other portions of the indicia 82 such as thedata field 88 and the logo 86. Thus the color stripe 90 and the datafield 88 may be printed simultaneously or substantially simultaneously.

As will be further discussed below, the data field 88 representsauthentication data that is also represented by the color stripe 90.That authentication data may, for example, be presented at apredetermined part (indicated at 94) of the data field 88.

It should be understood that the indicia 82 may include other elements,which are not shown, and which may include one or more finder orreference marks, to aid in subsequent scanning and parsing of theindicia 82. In addition to or instead of representing the authenticationdata in a 2D barcode, the authentication data may be represented inother ways, such as a one-dimensional barcode, and/or alphanumericcharacters that are machine- and/or human-readable. The 2D barcode maybe omitted.

FIG. 5 shows the color stripe 90 in isolation, and on a larger scalethan in FIG. 4. (Because of the limitations of reproduction of drawingsin patent publications, the color stripe is not in actuality shown incolor.) The color stripe may include gaps 96, each near a respective endof the color stripe. The gaps 96 may be used during subsequent analysisof the color stripe as reference points. In other embodiments, the gaps96 may be omitted, or may be supplemented or replaced by other referencemarks, which are not shown.

In some embodiments, one or more color components of the color stripe 90may exhibit variations or gradients along the length of color stripe 90to represent authentication data. In some embodiments, the variationsmay be continuous and/or periodic, such as sinusoidal variations. Insome embodiments, sinusoidal variations of one color component may besuperimposed upon each other.

In some embodiments, a linear gradient or linear gradients in a colorcomponent may be exhibited along at least a portion of the length of thecolor stripe. The slope of the gradient in such a case may be employedto represent authentication data.

In some embodiments, a variation in color component along at least aportion of the length of the color stripe may take the form of asinusoid impressed on a linear gradient. In such a case, one or more ofthe slope of the linear gradient, and the wavelength, amplitude andphase of the sinusoid may be used to represent authentication data.

It should be understood that the appearance of the color stripe, and theauthentication data represented thereby, may vary from indicium toindicium, and from embodiment to embodiment.

FIG. 6 graphically illustrates an example of variations in intensity intwo color components that may be implemented in a particular colorstripe in some embodiments. In FIG. 6, the horizontal axis representsdisplacement along the length of the color stripe, and the vertical axisrepresents variation in color intensity. The solid-line curve 98represents variation in a green color component, and the dashed-linecurve 102 represents variation in a red color component. It will beobserved that both red and green color component variations aresinusoidal along the length of the color stripe. The red color componentvariation is a relatively large amplitude, large wavelength variation,that may be readily visible to the naked eye. The green color componentvariation is a relatively low amplitude, small wavelength variation,that may not be readily visible to the naked eye. The authenticationdata, in this example, may be represented by one or more of phase,amplitude and wave-length of either or both of the red and green colorcomponent variations. The low amplitude, small wavelength greenvariation may be particularly difficult to counterfeit.

FIG. 7 is a flow chart that illustrates a process by which one or morepostage stamps, like the stamp 80 shown in FIG. 4, may be printed inaccordance with principles of the present invention. The processillustrated in FIG. 7 includes process steps performed by the postageindicia printer 12 or by the administrative server 14, or by the printer12 and the server 14 operating in cooperation with each other.Accordingly, FIG. 7 is illustrative of software processes that controlthe printer 12 and the server 14 in accordance with principles of thepresent invention. The process illustrated in FIG. 7 includes processsteps performed by the postage stamp printing apparatus 10. These stepsare performed by the printer 12 and the administrative server 14. Thepreferred division of the steps is described in the following.

Initially in the process of FIG. 5 is step 104, at which the postageindicia printer 12 (FIGS. 1 and 3) initiates a data communicationsession with the administrative server 14 (FIGS. 1 and 2). This may bedone, for example, by the postage indicia printer 12 dialing up theserver 14 and engaging in a handshaking procedure with the server 14.The purpose of the communication session is to obtain authorization fromthe server 14 for the printer 12 to print one or more stamps, and alsofor the printer 12 to receive from the server 14 data to be used inprinting the stamps. (In an alternative embodiment, the printer mayreceive the data to be used in printing the stamps via a connection to aPC and the Internet.)

Next in the process of FIG. 7 is step 106, which in some embodiments mayprecede, or may occur simultaneously with, step 104. At step 106, theprinter 12 determines a series of units of authentication data to berepresented in the color stripes in respective stamps for whichauthorization is to be received from the server 14. In some embodiments,the printer 12 may determine the number of stamps for whichauthorization is to be requested. This number of stamps (as well as thedenominations of the stamps, e.g.) may be determined based on input froma user of the printer 12. The printer 12 (for example, by operation ofthe print head controller 60, FIG. 3) may then refer to units ofauthentication data in the ROM 62 on the basis of an index value storedin the RAM 68. The index value may point to an address in the ROM 62which contains the first of the units of authentication data. In otherembodiments, the ROM 62 may be omitted, and the printer 12 may generatethe authentication data by a random process, or by a pseudo-randomprocess that uses the serial number of the printer 12 as an input. Inother embodiments, the user may request a number of stamps of variousdenominations through an Internet web service linked to theadministrative server 14.

In any event, at step 108 the printer 12 transmits to the server 14 theauthentication data to be included in the stamps for which authorizationis being requested. This may be done, in part, by reading outauthentication data from the ROM 62 based on the index value referred toabove. After reading out the authentication data and transmitting theauthentication data to the server 14, the index value may be updated topoint to the next address in the ROM 62 after the locations at which thetransmitted authentication data was stored.

At step 110, the server 14 generates image data that represents the datafields 88 of the stamps now being authorized by the server 14 forprinting by the printer 12. As part of the process step of generatingthe data field image data, the server 14 may encrypt the authenticationdata received from the printer 12 using a secret key held in the server14 and may then encode the encrypted authentication data to include theencrypted authentication data in the data for the data field. The datafield for each stamp to be printed by the printer 12 may thus representauthentication data encrypted and encoded by the server 12. In someembodiments, the authentication data may be encoded for inclusion in thedata field without encrypting.

Before, after or simultaneously with step 110 is a step 112, at whichthe server 14 initiates a charge to the customer's account for thepostage to be represented by the stamps now being authorized forprinting. For example, the server 14 may transfer a suitable quantity offunds from a deposit account maintained by the holder of the printer 12to an account for the benefit of a postal authority such as the U.S.Postal Service. In other embodiments, the server may initiate a chargeto a credit card account or another type of account maintained by theholder of the printer 12 at a financial institution.

After step 110, and either before, after or simultaneously with step112, is step 114, at which the server 14 downloads to the printer 12 thedata field image data generated by the server 14 at step 110. That is,the server 14 transmits the data field image data to the printer 12, andthe printer 12 (e.g., the modem 70, the print head controller 60 and theRAM 68) receives the data field image data from the server 14. The datafield image data for each stamp of the batch of stamps being authorizedmay be stored in RAM 68 or non-volatile memory.

The downloading of data may also include image data that represents thelogo 86 to be included in the stamps. In another embodiment, the imagedata for the logo may have been loaded into the printer 12 at thefactory at which the printer 12 was manufactured. In still otherembodiments, the logo may be replaced with a custom or customizableimage selected by the holder of the stamp printer, and the image datafor such image may be downloaded from the server to the stamp printer orpre-stored in the stamp printer.

Following step 114 is step 116, at which the data communication sessionbetween the server 14 and the printer 12 is ended.

Step 118 follows step 116 in the process illustrated in FIG. 5. At step118, the printer 12 prints the stamps authorized by the server 14 duringthe session. (In other embodiments, the stamps may be printed during thesession. In still other embodiments, the printer prints some stampsduring the session with the server or afterward, while storingauthorization and data for further stamps in non-volatile memory forlater printing.) As part of printing each stamp, the first set 52 ofprint elements (FIGS. 3 and 4) of the print head 50 print a color stripe90 (FIG. 4) that represents the authentication data for the stamp inquestion stored. It will be understood that the authentication data hadbeen communicated to the server 14 during the session, and that theappropriate address in the ROM 62 is indicated by an index value storedin the RAM 68 or non-volatile memory. The printing of the color stripe90 by the first set 52 of print elements may be controlled by firstdriver software (not separately shown) which may be stored in RAM 68 orROM 62.

Also as part of the printing of the same stamp, the second set 54 ofprint elements of the print head 50 print the data field 88 of thestamp, including the authentication data represented by the color stripe90. It will be recalled that the authentication data had been encoded bythe server 14. The second set 54 of print elements 54 also prints thelogo 86 and other portions of the indicium 82. The printing performed bythe second set 54 of print elements may be controlled by second driversoftware (not separately shown) which may be stored in RAM 68 or ROM 62.Other methods of representing the authentication data could also be usedin addition to or instead of the two dimensional barcode shown in FIG.4.

It will be appreciated that the components and/or the layout of theindicium 82 may be changed. For example, the location of the colorstripe 90 in the indicium 82 may be changed. The data field 88 may takea form other than a two-dimensional barcode, and the logo 86 may beomitted.

FIG. 8 is a block diagram that illustrates a stamp reading andverification device 120 provided according to principles of the presentinvention.

The stamp verification device 120 of FIG. 6 includes a scanner 122 thatis arranged to scan a postage stamp 80 to capture a color image of theindicium 82 (FIG. 4, not separately shown in FIG. 8) from the postagestamp 80. (At the time of scanning by the verification device 120, thestamp 80 may be affixed to a mail piece, which is not separately shown.)The device 120 also includes an analysis portion 126 which is coupled tothe scanner 122 to receive from the scanner 122 image data which isgenerated by the scanner 122 and represents the image of the indicia.The image data is represented by block 128 in the analysis portion 126.The image data block 128 may comprise, for example, storage and/orpreliminary analysis of the image data. The analysis portion 126includes a data field reading (e.g., 2D barcode reading) block 130 and acolor stripe analysis block 132, both of which operate on the colorimage data of block 128. The analysis portion 126 further includes averification processing portion block 134 which receives data, includingauthentication data read from the data field 88 by the data fieldreading block 130 and authentication data extracted from the colorstripe 90 by the color stripe analysis block 132.

In some embodiments, the stamp verification device 120 may also includea spectral analysis block 136 (shown in phantom) to determine at leastone spectral characteristic of the stamp 80 on the basis of the imagedata from the image data block 128, and to provide a result of thespectral analysis to the verification processing portion block 134.

In some embodiments, the scanner 122 may be a conventional high-qualityscanner, such as the Epson “Expression” model 1680. Image data generatedby the scanner 122 may be provided in raw form to the color stripeanalysis block 132 to facilitate reliable detection of color componentvariations by the color stripe analysis block 132. In other embodiments,the image data generated by the scanner 122 may be pre-processed byconventional driver software, such as the “VueScan” driver availablefrom Hamrick Software, Phoenix, Ariz.

Operation of the stamp verification device 120 will now be describedwith reference to FIG. 7, which is a flow chart that illustrates anindicium reading and verification process performed by the device 120.

The process of FIG. 7 begins with a step 140 at which the scanner 122scans the stamp 80. Then, at step 142, the resulting digital image datais stored in the image data block 128. At step 144, the color stripeanalysis block 132 detects variations in color components along thelength of color stripe 90, on the basis of the image data stored in theimage data block 128, to extract authentication data from the colorstripe 90.

At step 146, the data field reading block 130 reads the data field 88(as represented in the image data stored in image data block 128) toread authentication data from the data field 88. The reading of theauthentication data by the data field reading block 130 may includedecrypting the authentication data. The decrypting may involve using apublic key and may verify that the authentication data encoded in thedata field 88 was generated by the administrative server 14 using thesecret key referred to in connection with step 110 of FIG. 7.

Continuing to refer to FIG. 7, at step 148, the authentication dataextracted from the color stripe by the color stripe analysis block 132and the authentication data read from the data field 88 by the datafield reading block 128 are compared by the verification processingportion block 134. A decision block 150 may follow or form part of step148. At decision block 150, it is determined whether the authenticationdata extracted from the color stripe and the authentication data readfrom the data field match. If so (and if it is determined at decisionblock 152, shown in phantom, that the stamp 80 exhibits a properspectral response for the authorized stock on which stamps are to beprinted), the stamp 80 may be considered to be authenticated (step 154).If the authentication data extracted from the color stripe and theauthentication data read from the data field are determined not to match(or if the stamp 80 does not exhibit the proper spectral response), thestamp 80 may be found to be counterfeit (step 156).

With a system as described herein, including printing of a color stripein a postage indicium to form a postage stamp printed on demand by apersonal postage stamp printer, along with corresponding authenticationdata encoded as part of a data field that is separate from the colorstripe, and analyzing the color stripe and reading the data field toconfirm that the authentication data from the data field matches theauthentication data from the color stripe, authentication of a postagestamp that is printed on demand can be facilitated and automated, andcounterfeiting of such postage stamps can be detected and deterred.Moreover, with the authentication of a postage stamp by comparingauthentication data from the color stripe to authentication data in thedata field, it may be the case that the stamp verification device doesnot require access to a central database, thereby significantly reducingthe cost and increasing the convenience of the counterfeit-preventionsystem. With this system, it also may not be necessary to account forblank stamp printing stock. Furthermore, a color stripe as describedherein may present significant technical challenges to a would-becounterfeiter.

In some embodiments, the inputs for the data field reading block 130 andthe color stripe analysis block 132 need not be obtained via a sharedscanner or a shared image data store. For example, data field readingand color stripe analysis may proceed in separate channels.

A stamp authentication device in accordance with some embodiments mayread other data from the stamp to be authenticated in addition to theauthentication data described above, and may perform other tests inaddition to comparing authentication data extracted from the colorstripe with authentication data read from the data field and detecting aspectral response of the stamp.

In some embodiments, a color stripe and a data field which includescorresponding authentication data may be included in an indicium printed(by a postage meter, for example) directly on a mail piece (envelope) orotherwise used for purposes other than printing a postage stamp ondemand from a personal postage stamp printer. Thus, the verificationprocess described herein may be employed to verify postage meter indiciaas well as postage stamps printed on adhesive stock, with or withoutpictorial images as part of the postage indicia.

The order in which process steps are described herein and/or indicatedin the drawings is not meant to imply a fixed order of steps, and it iscontemplated that the process steps may be performed in any order thatis practicable.

In some embodiments, the stamp printer may generate image data for thedata field (e.g. 2D barcode) on the basis of encrypted authenticationdata received from the server.

A color stripe as described herein may be printed as a security elementin other types of documents besides postage meter indicia or postagestamps printed on demand. Such a color stripe may be printed onsubstrates other than postage stamp stock or envelopes. Authenticationdata may also be represented by color component gradients in colorfields that are not in the shape of a stripe.

The words “comprise,” “comprises,” “comprising,” “include,” “including,”and “includes” when used in this specification and in the followingclaims are intended to specify the presence of stated features,elements, integers, components, or steps, but they do not preclude thepresence or addition of one or more other features, elements, integers,components, steps, or groups thereof.

A number of embodiments of the present invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention.Accordingly, other embodiments are within the scope of the followingclaims.

1. A method incorporating authentication data into a value indicia of amailpiece comprising: (A) scanning a color stripe; (B) generating colorgradient data indicative of at least one characteristic of a variationin intensity of at least one color component along a length of the colorstripe. the color gradient data including a color region representingthe authentication data by a substantially continuous sinusoidalvariation of at least one color component of the color region, the atleast one color component being represented by at least one of awavelength, amplitude and phase variation.
 2. The method according toclaim 1, further comprising: (A) reading a barcode adjacent to the colorstripe to generate barcode data; and (B) comparing the barcode data withthe color gradient data.
 3. The method according to claim 2, wherein thecolor stripe and the barcode are both part of a postage meter indicia,and the comparing step is to authenticate the postage meter indicia. 4.The method according to claim 3, wherein the barcode is atwo-dimensional barcode.
 5. The method according to claim 1, wherein thevariation is a sinusoidal variation and the at least one characteristicis at least one of wavelength, amplitude and phase of the sinusoidalvariation.